悬索桥主缆初应力对桥梁动力特性的影响

Effect of initial stress of main cable on dynamic characteristics of suspension bridge

为掌握主缆初应力对桥梁动力特性的影响,以悬索桥为例,采用静力非线性分析方法计算应力变化过程中悬索桥的跨中挠度、缆索轴力及加劲梁的轴力变化;将得到的内力作为结构的预加应力进行有预应力的模态分析.应用ANSYS软件进行分析,其中有限元建模时采用4种单元类型:空间梁单元BEAM4用于模拟加劲梁和塔;空间杆单元LINK10用于模拟主缆及吊杆;通过设定BEAM4和LINK10单元初应变进行有预应力的模态分析;采用MASS21单元模拟横隔板、吊杆锚固装置和桥面上的栏杆,并分别考虑质量和质量惯性矩的作用.分析表明,悬索桥主梁竖弯振动频率受主缆初应力的影响较大,而侧弯振动频率和扭转振动频率受此影响较小.该结果为同类桥梁的动力特性分析提供参考.

To grasp the effect of initial stress of main cable on dynamic characteristics of bridge, a suspension bridge is taken as an example. The mid-span deflection, axial load of cable and stiffened girder are calculated by static nonlinear analysis method; and the obtained internal force is taken as the pre-stress to analyze the mode analysis of structure with pre-stress. ANSYS is used to perform the analysis. Four types of elements are used for finite element modeling. The stiffened girders and pylons are simulated by space beam element BEAM4; the main cable and suspenders are simulated by space bar element LINK10; the mode analysis with pre-stress is performed by setting the elements of BEAM4 and LINK10; the bridge cross spacer, suspenders anchorage and deck railings are simulated by MASS21 and the effect of mass and mass moment is considered separately. The analysis indicates that the vertical bending vibration frequency of main beam of suspension bridge are affected greatly by initial stress of main cable, but the side bending vibration frequency and the twist bending vibration frequency are less affected by it. The results provide a reference for the analysis on the dynamic characteristics of similar bridges.